A subcutaneous firm nodule on scrotal skin: Cytological considerations

A 30-year-old patient presented with a solitary painless subcutaneous 3 × 3 cm nodule in the ventral aspect of the scrotum [Figure 1a] since 2 years without prior history of sexually transmitted disease, trauma, or inflammation of the scrotum. Fine-needle aspiration of the nodule showed an amorphous debris. The smears stained with May-Grunwald Giemsa and Papanicolaou stain showed findings shown in Figure 1b and c.

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Figure 1:

Solitary subcutaneous nodule (a) Cytology smear showed amorphous debris (b: May-Grunwald Giemsa, ×400); c: Papanicolaou, ×400; d: Zoomed area from c).

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Q1. What is the most likely diagnosis?

1. Calcified epidermal cyst

2. Necrotic debris

3. Scrotal calcinosis

4. Scrotal pilomatrixoma.

Answer:

Q1-C. Scrotal calcinosis.

The presence of the amorphous basophilic substance, that is, calcific deposits without any epithelial cells in fine-needle aspiration (FNAC) smears, favored diagnosis of calcinosis.^[1-4] The lack of epithelial cells in the FNAC smears helped in ruling out the possibility of a calcified epidermal cyst.^[1] The calcified debris is also reported in pilomatrixoma.^[5] FNAC of pilomatrixoma may show the presence of anucleated squames and basaloid cells, which were absent in the present case.^[5] A possibility of necrotic debris was ruled due to the lack of inflammatory background.

Q2: Which one generally is not considered as the cytological features of scrotal calcinosis?

1. Amorphous basophilic granular material

2. Presence of foreign body giant cells

3. Lymphocytes surrounding basophilic amorphous material

4. Presence of numerous epithelial cells.

The FNAC of scrotal calcinosis generally shows the presence of amorphous basophilic granular material.^[1-4] This material may be surrounded by lymphocytes and foreign body giant cells.^[4,5] The epithelial cells are usually absent in the cytological smears of scrotal calcinosis.^[1-4]

Q3. Which special stain is used to demonstrate calcium?

1. Periodic acid–Schiff (PAS)

2. von Kossa

3. Perl’s Prussian blue

4. Rhodanine stain.

Calcium tissue deposits can be identified by the presence of von Kossa-positive black masses.^[6] With the hematoxylin and eosin stain, calcium appears deep blue purple. PAS is a commonly used stain to detect polysaccharides such as glycogen and mucosubstances, which appears deep red (magenta). Perl’s Prussian blue stain is used to demonstrate iron deposits in tissues. Copper deposits are demonstrated by rhodanine stain, which gives a red to orange-red cytoplasmic granular positivity to elemental copper.

A definitive diagnosis of scrotal calcinosis can be made only on the basis of histology.^[6] In the present case, the subcutaneous nodule was excised, and histopathological examination showed lobules of amorphous calcified areas in the dermis. The lobules were surrounded by fibrosis; however, no surrounding foreign body reaction was observed [Figure 2]. The calcium deposits may be surrounded by lymphocytes and foreign body giant cell reactions. In some reports, foreign body reaction surrounding the calcific deposits was not seen.^[1]

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Figure 2:

Histopathology showed calcific deposits in desmis (H and E, ×100).

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Q4: Which of the following is not implicated in the pathogenesis of scrotal calcinosis?

1. Dystrophic calcification of scrotal epithelial cyst

2. Degeneration of the dartos muscle

3. Metastatic calcification secondary to metabolic derangement

4. Unknown.

The pathogenesis of scrotal calcinosis is still unknown.^[7] Various authors have put forth various hypotheses. The prominent among them is that scrotal calcinosis arises due to dystrophic calcification of the ruptured scrotal epithelial cysts.^[6] Authors have argued that there is some quality to the scrotal skin that leads to rapid resolution of epidermoid cysts with calcification.^[6] Another hypothesis proposes that scrotal calcinosis is a degenerative phenomenon involving the scrotal dartos muscle, leading to calcium deposit.^[2,6] The argument favoring the scrotal calcinosis idiopathic nature is that the basophilic calcified material within the dermis may or may not show foreign body granulomatous reaction, and none show evidence of epithelial lining.^[6] Metastatic calcification occurs secondary to metabolic derangements such as hypercalcemia or hyperphosphatemia.^[1] In the present case, they were normal.

There was no foreign body giant reaction around the calcific deposits or epithelial lining with normal levels of serum calcium, phosphorus, and parathormone in the present case. These findings favored an idiopathic etiopathogenesis in the present case suggesting a diagnosis of idiopathic scrotal calcinosis (ISC).